[en] The Karlsruhe Tritium Neutrino (KATRIN) experiment is a large-scale effort to probe the absolute neutrino mass scale with a sensitivity of 0.2 eV (90% confidence level), via a precise measurement of the endpoint spectrum of tritium β-decay. This work documents several KATRIN commissioning milestones: the complete assembly of the experimental beamline, the successful transmission of electrons from three sources through the beamline to the primary detector, and tests of ion transport and retention. In the First Light commissioning campaign of autumn 2016, photoelectrons were generated at the rear wall and ions were created by a dedicated ion source attached to the rear section; in July 2017, gaseous ^83mKr was injected into the KATRIN source section, and a condensed ^83mKr source was deployed in the transport section. In this paper we describe the technical details of the apparatus and the configuration for each measurement, and give first results on source and system performance. In conclusion, we have successfully achieved transmission from all four sources, established system stability, and characterized many aspects of the apparatus.

[en] After the KATRIN letter of intent in 2001 and the addendum to the LoI in 2002, this design report 2004 gives a detailed overview of the KATRIN experiment in its phase of building and testing of the first components. We critically assess the actual status in neutrino physics with respect to direct and indirect searches on the neutrino mass in particle physics and cosmology and the impact by KATRIN. The physical parameters as well as the schemes for the technical realization of the central experimental components and their status are reported. Having optimized the experimental configuration compared to the LoI, we anticipate a KATRIN sensitivity on the neutrino mass of m(ν_e) = 0.2 eV (90% C.L.) corresponding to a 5 σ discovery potential for m(ν_e) = 0.35 eV, based on a detailed assessment of systematic and statistical uncertainties. (orig.)

[en] In this work we present a keV-scale sterile-neutrino search with a low-tritium-activity data set of the KATRIN experiment, acquired in a commissioning run in 2018. KATRIN performs a spectroscopic measurement of the tritium β-decay spectrum with the main goal of directly determining the effective electron anti-neutrino mass. During this commissioning phase a lower tritium activity facilitated the measurement of a wider part of the tritium spectrum and thus the search for sterile neutrinos with a mass of up to 1.6 keV. We do not find a signal and set an exclusion limit on the sterile-to-active mixing amplitude of sin${}^2$θ < 5 × 10${}^{-<!--\; ???\; -->4}$ (95% C.L.) at a mass of 0.3 keV. This result improves current laboratory-based bounds in the sterile-neutrino mass range between 0.1 and 1.0 keV.

[en] During operation of high energy physics experiments a big amount of slow control data is recorded. It is necessary to examine all collected data checking the integrity and validity of measurements. With growing maturity of AJAX technologies it becomes possible to construct sophisticated interfaces using web technologies only. Our solution for handling time series, generally slow control data, has a modular architecture: backend system for data analysis and preparation, a web service interface for data access and a fast AJAX web display. In order to provide fast interactive access the time series are aggregated over time slices of few predefined lengths. The aggregated values are stored in the temporary caching database and, then, are used to create generalizing data plots. These plots may include indication of data quality and are generated within few hundreds of milliseconds even if very high data rates are involved. The extensible export subsystem provides data in multiple formats including CSV, Excel, ROOT, and TDMS. The search engine can be used to find periods of time where indications of selected sensors are falling into the specified ranges. Utilization of the caching database allows performing most of such lookups within a second. Based on this functionality a web interface facilitating fast (Google-maps style) navigation through the data has been implemented. The solution is at the moment used by several slow control systems at Test Facility for Fusion Magnets (TOSKA) and Karlsruhe Tritium Neutrino (KATRIN).

[en] The primary objective of the KATRIN experiment is to probe the absolute neutrino mass scale with a sensitivity of 200 meV (90% C.L.) by precision spectroscopy of tritium β-decay. To achieve this, a low background of the order of 10⁻² cps in the region of the tritium β-decay endpoint is required. Measurements with an electrostatic retarding spectrometer have revealed that electrons, arising from nuclear decays in the volume of the spectrometer, are stored over long time periods and thereby act as a major source of background exceeding this limit. In this paper we present a novel active background reduction method based on stochastic heating of stored electrons by the well-known process of electron cyclotron resonance (ECR). A successful proof-of-principle of the ECR technique was demonstrated in test measurements at the KATRIN prespectrometer, yielding a large reduction of the background rate. In addition, we have carried out extensive Monte Carlo simulations to reveal the potential of the ECR technique to remove all trapped electrons in a few ms with negligible loss of measurement time in the main spectrometer. This would allow the KATRIN experiment attaining its full physics potential.

[en] The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to determine the effective electron (anti)-neutrino mass with a sensitivity of 0.2eV/c${}^2$ by precisely measuring the endpoint region of the tritium β-decay spectrum. It uses a tandem of electrostatic spectrometers working as magnetic adiabatic collimation combined with an electrostatic (MAC-E) filters. In the space between the pre-spectrometer and the main spectrometer, creating a Penning trap is unavoidable when the superconducting magnet between the two spectrometers, biased at their respective nominal potentials, is energized. The electrons accumulated in this trap can lead to discharges, which create additional background electrons and endanger the spectrometer and detector section downstream. To counteract this problem, “electron catchers” were installed in the beamline inside the magnet bore between the two spectrometers. These catchers can be moved across the magnetic-flux tube and intercept on a sub-ms time scale the stored electrons along their magnetron motion paths. In this paper, we report on the design and the successful commissioning of the electron catchers and present results on their efficiency in reducing the experimental background.

[en] The Karlsruhe Tritium Neutrino (KATRIN) experiment will determine the mass of the electron neutrino with a sensitivity of 0.2 eV (90% CL) via a measurement of the β-spectrum of gaseous tritium near its endpoint of E₀ = 18.57 keV. An ultra-low background of about b = 10 mHz is among the requirements on reaching this sensitivity. In the KATRIN main beam line, two spectrometers of MAC-E filter type are used in tandem configuration. This setup, however, produces a Penning trap, which could lead to increased background. We have performed test measurements showing that the filter energy of the pre-spectrometer can be reduced by several keV in order to diminish this trap. These measurements were analyzed with the help of a complex computer simulation, modeling multiple electron reflections from both the detector and the photoelectric electron source used in our test setup. (paper)

[en] The KATRIN experiment is designed for a direct and model-independent determination of the effective electron anti-neutrino mass via a high-precision measurement of the tritium β-decay endpoint region with a sensitivity on m${}_{\mathrm{\nu <!--\; ??\; -->}}$ of 0.2 eV/c${}^2$ (90% CL). For this purpose, the β-electrons from a high-luminosity windowless gaseous tritium source traversing an electrostatic retarding spectrometer are counted to obtain an integral spectrum around the endpoint energy of 18.6 keV. A dominant systematic effect of the response of the experimental setup is the energy loss of β-electrons from elastic and inelastic scattering off tritium molecules within the source. We determined the energy-loss function in-situ with a pulsed angular-selective and monoenergetic photoelectron source at various tritium-source densities. The data was recorded in integral and differential modes; the latter was achieved by using a novel time-of-flight technique. We developed a semi-empirical parametrization for the energy-loss function for the scattering of 18.6-keV electrons from hydrogen isotopologs. This model was fit to measurement data with a 95% T${}_2$ gas mixture at 30 K, as used in the first KATRIN neutrino-mass analyses, as well as a D${}_2$ gas mixture of 96% purity used in KATRIN commissioning runs. The achieved precision on the energy-loss function has abated the corresponding uncertainty of σ(m${}_{\mathrm{\nu <!--\; ??\; -->}}^2$) <10${}^{-<!--\; ???\; -->2}$eV${}^2$ in the KATRIN neutrino-mass measurement to a subdominant level.

[en] The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to measure the absolute neutrino mass scale with an unprecedented sensitivity of 0.2 eV/c² (90% C.L.), using β decay electrons from tritium decay. The kinetic energy of the decay electrons is measured using an electrostatic integrating main spectrometer with magnetic adiabatic collimation and requires a certain magnetic field profile. For the control of the magnetic field in the main spectrometer area two networks of mobile magnetic field sensor units are developed and commissioned. The radial system is operated close to the outer surface of the main spectrometer whereas the vertical one is mounted along vertical planes left and right of the main spectrometer. The sensor setup can take several thousand magnetic field samples at a fine meshed grid, thus allowing to study the magnetic field inside the main spectrometer and the influence of magnetic materials in the vicinity of the main spectrometer.

[en] The KATRIN experiment will measure the absolute mass scale of neutrinos with a sensitivity of m_ν = 200meV/c² by means of an electrostatic spectrometer set close to the tritium β-decay endpoint at 18.6keV. Fluctuations of the energy scale must be under control within ±60mV (±3ppm). Since a precise voltage measurement in the range of tens of kV is on the edge of current technology, a nuclear standard will be deployed additionally. Parallel to the main spectrometer the same retarding potential will be applied to the monitor spectrometer to measure 17.8-keV K-conversion electrons of ^83mKr. This article describes the setup of the monitor spectrometer and presents its first measurement results